Non-binary seems like it could have several non-compatible meanings, so I wanted to list some of those meanings and see if there are any others out there I don't know.
One way I could think of non-binary is as being a kind of third gender category, like there are men, women, and non-binary people. In this sense of non-binary a butch woman who considers themselves a woman would not be non-binary because they are a woman.
Sometimes non-binary is used like "genderqueer" is sometimes used, as a generic description of anyone who doesn't fit perfectly in the narrow confines of the binary genders (i.e. men and women). In this sense a butch woman could see themselves as a woman, but also as genderqueer and non-binary, as they do not conform to binary gender norms for women.
Another way non-binary seems to be used (related to genderqueer in its historical context) is as a political term, an identity taken up by otherwise cis-sexual and even cis-gendered people who wish to resist binary gender norms and policing. In this sense even a femme cis-sexual woman might identify as non-binary. Sometimes this political identity label might come with a gender expression that cuts against the gender expectations for the assigned sex at birth, but it doesn't have to. (I recently met two people whose gender expressions matched their assigned sex at birth but who identified as non-binary in this political sense.)
I was wondering what other meanings of non-binary are out there, and how they are commonly used.
Note: gatekeeping what is "really" non-binary seems pointless to me, since I agree with Wittgenstein that "language is use".
I know people get heated about policing what a word means (and I am guilty of this myself), but in the interest of inclusion, pluralism, and general cooperation in our community I think we can find a way to communicate with overlapping and different meanings of a shared term.
I used to think of nonbinary as just a third box, but the more I've been exposed to nonbinary identities and just thinking a lot about it, it seems like falling for the binary trap again. I guess technically it's ternary, but the point is that discretizes gender again.
Imagine a survey asking for people's favorite color:
"Nonbinary" is akin to saying "Other", which isn't very descriptive. In a world where 95% of people pick blue or green, I suppose it is useful to say "I'm not one of those", but that serves mostly to preempt expectations, it doesn't actually say much about the person.
More complicated: what if my favorite color is a purplish blue? Is that blue? Is that other? People get confused when I flip flop between those two answers because they're thinking purely about the 3 answer choices rather than the entire color spectrum. My favorite color is actually quite clear and consistent, it's just the mapping to the limited answer choices that's confusing.
The 3 answer choices generally work for most people (even " other" is good as a very quick summary), but people frame their entire understanding of color through those answers rather than understanding the actual color science it's based on, that's the problem. Even among blue people, they prefer different shades.
So about the contradictory definitions: yeah, red is not the same as yellow, but they're both "other".